Doctor of Philosophy
As a powerful analytical technique, electrochemiluminescence (ECL) has found wide applications in the fields of bioanalysis and light-emitting devices. However, many ECL materials sustain the shortcomings of low ECL efficiencies. To better design novel materials with ECL enhancement, it is essential to investigate and the enhanced ECL mechanisms. In this thesis, ECL enhancements of various novel materials were analyzed utilizing ECL-voltage curves, potential pulsing experiments, ECL and photoluminescence spectroscopies, and other characterization methods. Specifically, two graphene quantum dots (GQDs) with different heteroatom doping were designed and synthesized. Structural characterizations and spectroscopies demonstrated that the heteroatom doping could change the surface states of GQDs and thus greatly improve their ECL performance. An N-annulated perylene diimide dimer, tPDI2N-hex as a graphene model compound with atomic precision, was found to have superior ECL efficiency due to the desired excited states in the absence of surface states. Without aggregation-caused quenching effect, an organic light-emitting diode (OLED) was also fabricated displaying bright orange-red emission with a low color temperature. Hydrogen bonding (H-bonding) was discovered to be a smart strategy to enhance ECL. Absolute ECL efficiencies of two iridium(III) complexes were determined and radical stability and reactivity were identified to be key factors influencing ECL behaviors. Then insights into the ECL of a H-bonding complex between an iridium(III) complex and an organic molecule was investigated. ECL of a bisindolylpyrrole derivative was significantly enhanced via supramolecular recognition of H2PO4- anion due to restriction of intramolecular rotations (RIR). ECL efficiencies of a series of silole compounds were determined to understand the ECL optimization via extended p-conjugated systems and bulky groups on Si mainly. ECL of two benzosilole films was discovered to be greatly augmented by means of crystallization-induced enhancement due to RIR. Finally, ECL of a multi-resonance thermally activated delayed fluorescence (MR-TADF) molecule was explored in some interesting aspect such as organic long-persistent ECL (OLECL) and TADF.
Summary for Lay Audience
Electrochemiluminescence (ECL) is a light emission process where electricity is applied to a luminescence molecule leading to light emission. In this manner, ECL has wide applications in chemo/bioanalysis and light-emitting devices. Many chemical materials, including organic molecules, inorganic complexes and nanomaterials, have been reported as ECL emitters. To better find and design strong ECL molecules, this thesis is focused on understanding the ECL fundamentals, reaction mechanisms as well as its enhancement.
Various novel materials were explored for their ECL performance, including graphene quantum dots, perylene diimide derivative, iridium(III) complexes, bisindolylpyrrole derivatives, silole compounds and a special molecule with the property of thermally activated delayed fluorescence. By means of electrochemistry, spectroscopy and modern instrumentation, their enhanced ECL was tuned and mechanisms were identified. It is anticipated to find their applications in many research fields such as chemo/bioanalysis and light-emitting devices.
Yang, Liuqing, "Analyzing Enhanced Electrochemiluminescence of Novel Materials" (2022). Electronic Thesis and Dissertation Repository. 8815.
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